1. Field of the Invention
This invention relates to apparatus for measuring the dynamic force exerted by a rotating shaft on a bearing and more particularly to a bearing force transducer system by which two bearing force and moment components can be simultaneously measured to provide a resultant measure of bearing force and moment exerted on a shaft without disrupting the operation of the rotating shaft.
2. Description of the Prior Art
In a conventional rotor or driven system a drive shaft coupled to a motor transmits a rotation to a member such as a rotor mounted on the shaft. Accordingly, the shaft is rotatably journalled in a frame by bearings. Conventionally, over a period of time of operation, the bearings may become worn and the shaft eccentrically supported by the bearing to the extent that static and dynamic loads are exerted on the shaft.
A number of solutions have been proposed to detect lateral movement of a shaft resulting in unbalance and eccentricity of the shaft rotating in the bearing. If this condition persists for a long period of time, fatigue and potential wear of the bearing can lead to improper operation of the machinery. It is known to use detectors to monitor the movement of a shaft mounted in bearings to obtain a measure of the wear on the shaft. By continually monitoring or detecting movement of the shaft, it is possible to measure the amplitude and frequency of the dynamic forces exerted on the bearing which will result in fatigue or wear on the machinery over a period of time.
Examples of devices for measuring the amplitude and frequency of dynamic force exerted on a rotating shaft journalled in a bearing are disclosed in U. S. Pat. Nos. 4,027,539 and 4,464,935. In each of these devices a sensor is mounted on the bearing. In U. S. Pat. No. 4,027,539 a load cell is mounted on the non-rotating portion of the bearing to sense the frequency and amplitude of movement of the shaft journalled in the bearing. The load cell extends into physical contact to sense the pressure generated by lateral movement of the shaft on the load cell within the bearing. With the embodiment disclosed in U. S. Pat. No. 4,464,935, a pair of detectors are supported by the bearing and protrude into the cavity containing the fluid formed by the bearing for receiving the shaft. In both of the above described embodiments, the load cells and sensors are located on two axes spaced at right angles to one another to provide a reading of the forces generated in X and Y axes.
It is also well known to utilize optical, magnet-inductive, and capacitive detectors for detecting movement of a shaft or rotor mounted in bearings. The magnetic detector consists of a magnetic component firmly fixed to the stator and is used to measure the air gap formed between a stator and a rotor. With the capacitive detector, a condensor is fixed to the stator and another is fixed to the rotor. With each of these devices as well as those described in the above-identified patents, the load cell or sensor upon detection of lateral movement generates an electrical signal which is transmitted to a control device which provide a readout of the total dynamic force exerted on the shaft at the point where the measurements are taken.
While it has been suggested by the prior art devices to monitor lateral displacement of a shaft supported in a bearing during operation of the associated machinery, the known devices require substantial modification to the machinery to accommodate support of the detector on the bearing structure so that the probe of the detector is in close contact with the shaft. Therefore, there is need for a system to measure dynamic displacement of a shaft supported in a bearing which does not contact the shaft or require the journal or bearing to be materially altered to support the detector. The detector must be capable of selective movement around the axis of the shaft to provide a plurality of readings at selected angles in order to generate a resultant measure of the shaft displacement.